Stencil screen frame



Jan- 26, 1965 H. L. MILLER ETAL STENCIL SCREEN FRAME 2 Sheets-Sheet 1Filed May 28, 1963 S N Y R M m a 2a x m EL T ID wm mR m mm m Y WMM HT mm9.

3 mm mm Jan. 26, 1965 H. L. MILLER ETAL STENCIL SCREEN FRAME 2Sheets-Sheet 2 Filed May 28, 1963 INVENTORS. HENRY L. MILLER THOMAS;AMSDEN their ATTORNEY United States Patent() Filed May 28, 1963, Ser.No. 283,792 11 Claims. (ill. 101-4271) This invention relates to a framefor supporting a stencil screen, and more particularly to a unitaryframe having contiguous stencil screen retaining means.

One major problem associated with prior art stencil 'screen framesconcerns their ability to maintain the stencil screen in a tautcondition. Most prior art stencil screen frames are comprised of twoseparate types of components, namely, theframe itself and one or moreextrinsic elements which are used to secure the stencil screen to "theframe. Theseextrinsic elements may comprise, as for example, a cord fortying the stencil screen to the frame or wedge members which are adaptedto be inserted into recesses in the frame in such a manner that thestencil screen is simultaneously stretched. It should be noted,hcweventhat these methods of securing the stencil screen to the frameare time consuming and more important, there is no positive assurancethat the stencil screen will remain on the frame while the frame isbeing used in a printing process.

Accordingly, the primary objects of the present invention include:

To provide a unitary stencil screen frame having novel contiguous meansfor securing the stencil screen to the frame;

To provide a unitary stencil screen frame having novel contiguous screensecuring means which assures a positive connection between the stencilscreen and the frame;

To provide a unitary stencil screen frame having novel contiguous screensecuring means whereby a stencil screen may be quickly and easilysecured to the frame;

To provide a unitary stencil screen frame having resilient side memberswhich maintain a stencil screen in a taut condition; and

To provide a stencil screen frame which is lightweight and disposable. pI These and other objects and advantages of the present invention willbecome apparent from the following detailed description by reference tothe accompanying draw- 4-4 of FIG. 1, illustrating one wall member ofthe present stencil screen frame;

FIG. 5 is a cross-sectional view, taken along the line 5-5 of FIG. 1,illustrating another wall member of the present stencil screen frame;

FIGS. 6 and 7 are fragmentary cross-sectional views similar to FIG. 3and illustrating the means by which a stencil screen is secured to thepresent frame;

FIG. 8 is a bottom plan view of an alternative embodiment of the presentstencil screen frame;

FIG. 9 is a cross-sectional View taken along the line 9-9 of FIG. 8;

FIG. 10 is a top plan view of a further alternative embodiment of thepresent stencil screen frame;

FIG. 11 is a cross-sectional view, taken along the line "ice lib-11 ofFIG. 10, further illustrating the embodiment of FIG. 10;

FIG. 12 is a top plan view of a second frame used in conjunction withthe stencil screen frame of FIG. 10;

FIG. 13 is a cross-sectional view taken along the line 13-43 of FIG. 12;

FIG. 14 is a fragmentary isometric view illustrating a clamping meansused in conjunction with a metal stencil screen mounted on the preferredembodiment of the present stencil screen frame; and

FIG. 15 is a cross-sectional view, taken along the line 15-1 of FIG. 14,further illustrating the clamping means of FIG. 14.

According to the preferred embodiment of the present invention, aunitary, lightweight stencil screen frame is provided having a pluralityof wall members which define an opening in the frame. The stencil screenframe preferably is formed from lightweight, resilient, plasticmaterials whereby it is resistant to the deteriorating efiects ofpresent day printing inks. Furthermore, the present stencil screen isrelatively inexpensive and therefore is of the disposable type. The wallmembers have outer edges which lie in substantially the same plane.Fusible means is provided which preferably is contiguous with the outeredges of the wall members. The fusible means serves to secure thestencil screen to the frame. The fusible means preferably comprises abead of thermoplastic material which may be melted by the application ofheat and which, when melted, will fuse with the stencil screen to securethe same to the frame.

In the preferred embodiment, the frame includes a pair of opposed wallmembers which preferably are normally outwardly bowed. Since the frameis formed from a resilient material, these wall members are adapted tobe bent or bowed inwardly when the prestretched stencil screen issecured to the frame. When the inwardly bent wall members are releasedthey tend to move outwardly into their normally outwardly bowed positionwhereby the stencil screen is stretched and maintained in a tautcondition.

According to an alternative embodiment of the present invention, theoutwardly bowed wall members are each :provided with an arcuate lengthof spring steel or the like which serves to reinforce the wall memberswhereby more force is provided in maintaining the stencil screen in ataut condition.

According to a further alternative embodiment of the present invention,aunitary stencil screen frame is provided having a plurality ofresilient wallmembers which define an opening in the frame. In thisembodiment, all the wall members are normally straight. The stencil issecured to the frame in loose overlying relation with the opening. Arigid frame also is provided which is insertable into the opening of thestencil screen frame. The rigid frame has a pair of outwardly bowed,opposed wall members which engage and outwardly bow the resilient wallmembers of the stencil screen frame thereby stretch- .20. The frame 2tcomprises a plurality'of side members 22, 24, 26 and 28. The lsidemembers 22, 24 comprise one pair of opposed side members each of whichis normally outwardly bowed. The side members 22, 24, 26 and 28 definean opening 3b in the stencil screen frame 20 which is covered by astencil screen when the frame 20 is used in a printing process. As bestseen in FIG. 2, the side members 22, 24, 26 and 28 have outer edges 32all of which lie in substantially the same plane.

Referring to FIGS. 1 and 4, the side member 22 preferably has anL-shaped transverse cross section and comprises a vertical wall member34 and a flange member 36 which projects laterally therefrom. The sidemember 22 also includes a plurality of rib members 38 which serve toreinforce the side member 22 and maintain its L-shaped configuration.

Referring to FIGS. 1, 2 and 5, the side member 24 preferably has asimilar L-shaped transverse cross-section and comprises a vertical wallmember 34 and a flange member 4t) which projects laterally therefrom.The side member 24 also includes a plurality of rib members 42 whichserve to reinforce the side member 14 and maintain its L-shapedconfiguration.

Referring to FIGS. 1 and 2, the side members 26, 28 each include avertical wall member 34 and a flange member 44a, 4412, respectively.Reinforcing rib members 46 extend between the vertical Walls 34 and theflange members 44a, 44b and serve to maintain the L-shaped configurationof the side members 26 and 28. The flange member 44a is provided with anopening 48 while the flange member 44b is provided with a slot 5th. Theopening 48 and the slot 50 provide for securing the frame 20,

as for example, to support arms 51 one of which is shown in phantomoutline for subsequent securement on a stenciling machine (not shown) indecorating relation with an object to be decorated.

The frame 2% preferably is formed from a lightweight, resilient, plasticmaterial which has the property of being 7 thermoplastic. The frame 20preferably is formed from the crystalline form of polypropylene.Alternatively, the frame 20 could be formed from other thermoplasticmaterials such as molded nylon, polyacetyl which is a product sold underthe trade name Delrin, or polycarbonate which is a product sold underthe trade name Lexan.

As can best been seen in FIG. 1, the flange members 44a, 44b of the sidemembers 26 and 28, respectively, arerelatively wide flanges whichcooperate with the rib members 46 so that the side members 26 and 28 aresubstantially rigid. On the other hand, the flange members 36 and 40 ofthe side members 22 and 24, respectively, are narrow whereby the sidemembers 22 and 24 are resilient and may be bent. Since the side members22 and 24 are resilient, they may be displaced inwardly, that is, towardeach other. The side member 24 has been illustrated. in phantom outlinein an inwardly displaced position which is designated by the numeral24'. The resiliency of the side members 22, 24 is an important featureof the present frame 20 which will be more fully described later in thespecification.

As hereinbefore stated, the present invention provides a novel screenretaining means which is contiguous with the stencil screen frame 20.Referring now to FIG. 3, the upper portion of one of the wall members 34is illustrated. The outer edge 32 thereof preferably includes a bead 52which is contiguous therewith and which preferably is centrally disposedthereon. ,The bead 52 preferably extends along the entire length of eachof the wall members 34, that is, it extends continuously around theperiphery of the opening 3d. As will be remembered,

the frame 20 preferably is formed from a thermoplastic material. Hence,the bead 52 serves as a fusible means for securing a stencil screen tothe frame 20. Alternatively, the frame 20 could be formed without thebead 52. In this instance, the outer edge 32 which would serve as afusible means for securing a stencil screen tothe frame 20;

A description of the ease by which the stencil screen 7 4 may be securedto the frame 20 will now follow with reference to FIGS. 1, 6 and 7.

In FIG. 6, the wall member 34 of the side member 24 is shown in theinwardly displaced posit-ion illustrated in phantom outline in FIG. 1.The direction of the displacement is indicated by the arrow numbered 54.The side member 24 is maintained in this inwardly displaced position byany suitable means such as a jig (not shown) until the stencil screen issecured to the frame 20. A prestretched stencil screen 56 is placed overthe outer edge 32, as shown, in overlying relation with the opening 30in the frame 20. The bead 52 may be melted by the application of heatthrough the stencil screen 56. The

required heat may be supplied by any suitable heating implement. Whenthe melted bead 52 cools, it will fuse, as indicated at 52' in FIG. 7,with the stencil screen 56 to secure it to the frame 20.

After the stencil screen 56 has been positively secured to the frame 20,the side member 24 is released whereupon it will tend to move outwardlyto assume its normally outwardly bowed position illustrated in fulllines in FIG. 1. The direction of displacement is indicated in FIG. 7 bythe arrow numbered 58.

It should be noted that preferably both of the side mem- 1 bers 22 and24 are displaced inwardly, as for example,

by use of a jig before securing the stencil screen 56 to the frame 20.When they are released they will tend to move outwardly whereby thestencil screen 56 is stretched and maintained in a taut condition.Alternatively, only one of the side members need be displaced inwardlybefore securing the stencil screen 56 to the frame 20. As illustrated inFIG. 1, the side member 24 is relatively more flexible than the sidemember 22 by virtue of its narrower flange member 40. As specificallyillustrated in FIG. 1, the side member 24 will undergo considerableinward displacement before the side member 22 may be displaced inwardly.It should be evident then that although only one of the side members isdisplaced inwardly, the final resulting stencil screen assembly. willhave a stencil screen which is maintained in a taut condition at alltimes.

Reference is now directed to FIGS. 8 and 9 wherein an alternativeembodiment of the present stencil screen frame is illustrated andidentified by the numeral 60. Corresponding numerals will be employed toidentify corresponding parts already described.

In this embodiment, the side members 22, 24 include a slot 62 (see FIG.9) extending along substantially their entire length and into thevertical walls 24 thereof. Within'each of the slots 62, there isprovided a spring means which preferably comprises an arcuate strip 64of spring steel which serves to bow the wall members 22, 24 intheoutward direction illustrated. The arcuate strips 64 serve the furtherpurpose of increasing the outwardly directed force used in stretching astencil screen as hereinabove described. As can be seen in FIG. 8, eachof the arcuate strips 64 are shorter than slot 62 whereby a space 65 isprovided at each 'end into which the arcuate strips 64 move when theside members 22, 24 are bowed inwardly. In this embodiment, then, thereis provided a positive means for bowing the wall members 22, 24 in anoutward direction.

Reference is now directed to FIGS. 10 to 13 wherein a furtheralternative embodiment of the present stencil screen frame isillustrated. Corresponding numerals will be employed to identifycorresponding parts already described.

In FIGS. 10 and 11 there is illustrated a stencil screen frame 66 havingwall members 22', 24' which are normally straight as shown. With theexception of the straight wall members 22, 24, the stencil screen frame66 is identical to the stencil screen frame 26 of the preferredembodiment. V

The stencil screen frame 66 is adapted for use in conjunction with arigid frame 68 which is illustrated in FIGS. 12 and 13. The rigid frame68 preferably is formed from metal and includes side walls 70, 72, 74and 76.

As can be seen in FIG. 13, the side wall '70 has a rigid L-shapedcross-section. It should be noted that the remaining side walls 72, 74and 76 also have the same L- shaped cross-section. The side walls74 and76 have a flange member 7 8 extending therefrom each of which has a pairof apertures 80, 82. The apertures 80 are so positioned whereby they areconcident with the aperture 48 and the slot 50 in the flange member 44aand 44b respectively of the stencil screen frame 66 (see FIG. andcooperate therewith in receiving fasteners (not shown) for securing thestencil screen frame 66 to the rigid frame 68. The apertures 82 in theflange members 78 are adapted to receive fasteners (not shown) forsecuring the rigid frame 63 to support arms 84 (one shown in phantomoutline) :of a mounting bracket.

When using the stencil screen frame 66, the stencil screen 56 is securedto the outer edges 32 by employing the bead 52 as described inconnection with the preferred embodiment. However, in this instance, thestencil screen 56 is secured in a loose overlying relation with theopening 30 as illustrated in FIG. 11, i.e., the stencil screen 56 isallowed to sag slightly. The stencil screen frame 66 is then .fittedover the rigid frame 68 whereupon the arcua-te side walls 70, 72 of therigid frame 68 force the resilient wall members 22, 24' of the stencilscreen frame 66 to assume a similar arcuate shape. By bowing theresilient wall members 22, 24' in an outward direction, the stencilscreen 56 (see FIG. 11) is stretched into a taut condition and is readyto be used.

The cooperating stencil screen frame 66 and rigid frame 68 areparticularly adaptable for use with stencil screens which are easilypunctured when in a stretched condition. That is to say, some stencilscreen materials are relatively thin and must be handled with some care.Hence, by securing this type of stencil screen to the stencil screenframe 66 in a loose manner as illustrated in FIG. 11, the stencil screenframe may be handled without fear of damaging the stencil screen since,by virtue of its sagging condition, a give in the material is provided.When the screen is to be used, the stencil screen frame 66 is mounted onthe rigid frame 68 whereby the stencil screen is stretched in a tautcondition ready for use.

It should be understood, however, that this embodiment may be employed,with equal utility, to support any other type of stencil screen.

Referring now to FIGS. 14 and 15, the present stencil screen frames 26,60 or 66 may be used to support a metal stencil screen to which isapplied an electric current for heating the screen. In order to supportthis type of screen, some means must be provided for connecting themetal screen to a source of electric current. As can be seen in FIG. 14,a stencil screen frame is illustrated which is identified by the numeral86. The stencil screen frame 86 may comprise any one of the stencilscreen frames 20, 60 or 66 each of which is used as hereinbeforedescribed. A metal stencil screen 88 is secured to the stencil screenframe 86 in the manner heretofore described and is maintained in a tautcondition ready for use. The metal stencil screen 88 has an end portion90 which extends from each end thereof.

A pair of plates 92, 94, comprising cooperating means, are shownclamping the end portion 90 of the metal stencil screen 88 therebetween.The plates 92, 94 prefer- 6 FIG. 15, the plate 94 includes projectinglugs 104 which serve to maintain the plates 92, 94 spaced from thestructure 100 whereby air is allowed to circulate around the plates 92,94 for cooling the same.

At the extreme end of the fastener 96 there is provided a washer 106upon which rests a contact 108 of an electrical conductor 119. A wingnut112 is threaded onto the fastener 96 and serves to clamp the plates 92,94 in a rigid position and to secure the contact 108 to the fastener 96.Thus the fastener 96 serves to conduct the electric current brought inby the conductor 110.

It should be noted at this point, that the metal stencil screen 88 hastwo end portions both of which are clamped between similar pairs of theplates 92, 94 as illustrated in FIGS. 14 and'15. Thus, an electriccurrent is passed through one set of the plates 92, 94, the metal screen88 and another set of the plates 92, 94 at the other end of the metalstencil screen 88.

As illustrated in FIG. 14, the plates 92, 94 extend for substantiallythe entire length of the distance between the rib members 46. Ifdesired, the plates 92, 94 may be made to extend for a distance equal tothe width of the metal stencil screen 88 by providing a notch in the ribmembers 46 at an appropriate height. This may be desirable in case theelectrical current is not evenly distributed over the entire width ofthe screen 88 since an uneven distribution of the electric current maycause hot spots which would melt the screen and/ or the stencil screenframe 86.

Although the invention has been shown in connection with certainspecific embodiments, it will be readily apparent to those skilled inthe art that various changes in form and arrangement of parts may bemade to suit requirements without departing from the spirit and scope ofthe invention.

We claim as our invention:

1. A generally rectangular stencil screen frame comprising a pluralityof generally flattened, resilient wall members defining an opening insaid frame, one opposed pair of said wall members being substantiallyrigid, the remaining opposed pair of side wall members being normallyoutwardly bowed, means integral with said frame for securing a stencilscreen to said wall members in overlying relation with said opening,said wall members being substantially perpendicular to the plane of saidstencil screen and cooperating therewith to define a well for receivinga printing medium, said remaining opposed pair of said wall membersbeing adapted to be flexed inwardly while said stencil screen is securedto said frame, said remaining opposed pair of said wall members whenreleased serving to maintain said stencil screen in a tent condition.

2. A generally rectangular stencil screen frame comprising a pluralityof generally flattened wall members, one opposed pair of the wallmembers being substantially rigid, at least one wall member of theremaining pair of opposed wall members being a normally outwardly bowedwall member formed from resilient material, said Wall members definingan opening in said frame, means for securing a stencil screen to saidwall members in overlying relation with said opening, said wall membersbeing substantially perpendicular to the plane of said stencil screenand cooperating therewith to form a well for receiving a printingmedium, said normally outwardly bowed wall member being adapted to beinwardly flexed when said stencil screen is secured to said frame, saidnormally outwardly bowed wall member when released serving to maintainsaid stencil screen in a taut condition.

3. In a stencil screen assembly, the combination comprising a stencilscreen frame comprising a plurality of resilient, generally flattenedwall members defining an opening in said frame, said wall members beingnormally straight, a stencil screen secured to said wall members inloose overlying relation with said opening, and means insertable Withinsaid opening for bowing at least one of said wall members outwardlywhereby said stencil screen is stretched into a taut condition, saidwall members being substantially perpendicular to the plane of saidstencil screen when in its taut condition and cooperating therewith todefine a well for receiving a printing medium, said means insertablewithin said opening allowing said opening to be free of interferingmatter.

4. A generally rectangular stencil screen frame comprising pairs ofopposed side members, one opposed pair of the side members beingsubstantially rigid, at least one of the side members of the'remainingpair of opposed side members being resilient and normally outwardlybowed, fusible means integral with at least one pair of opposed sidemembers for securing a stencil screen to said frame, the normallyoutwardly bowed side member being adapted to be inwardly flexed intosubstantially parallel relation With the opposed side member when saidscreen is fused to said frame, said outwardly bowed member when releasedserving :to maintain said screen in a taut condition.

5. A stencil screen frame of one-piece molded construction, said framebeing molded from a resilient, thermoplastic material and comprisingpairs of generally flattened, opposed wall members defining an openingin said frame, a flange member integral with at least the wall membersof one of said pairs of opposed wall members, said flange membersprojecting outwardly from said opening, and a plurality of rib membersdisposed exteriorly of said opening and integral with said flangemembers and said wall members, one of said flange members being narrowerin width than the other of said flange members whereby the wall memberassociated with said one of said flange members is relatively moreflexible than the wall member associated with the other of said flangemembers.

6. A generally rectangular stencil screen frame comprising aplurality ofgenerally flattened wall members defining an opening in said frame, oneopposed pair of said Well members being substantially rigid, at leastone wall member of the remaining opposed pair of wall members beingresilient, said one Wall member having a slot formed therein whichextends throughout substantially its entire length, resilient meanscarried within said slot for maintaining-said one wall member in anoutwardly bowed condition, and means for securing a stencil screen tosaid frame in overlying relation with said opening, said one wall memberbeing adapted to be inwardly bowed while said stencil screen is securedto said frame, said one wall member when released serving to maintainsaid screen in a taut condition.

7. The stencil screen frame of claim 6 wherein said resilient meanscomprises an arcuate length of spring steel.

8. A stencil screen assembly comprising in combination: a generallyrectangular frame having pairs of opposed side members defining anopening in said frame, said frame being molded from resilient,thermoplastic material, a

stencil screen secured to said frame in overlying relation with saidopening by liquefying and solidifying portions of said frame, one pairof said opposed side members being substantially rigid, the second pairof opposed side members being normally outwardly bowed side memberswhich are adapted to be flexed inwardly while said stencil screen issecured to said frame, said normally outwardly bowed side members whenreleased serving to maintain said stencil screen in a taut condition.

9. A stencil screen assembly comprising in combination: a generallyrectangular frame having pairs of opposed side members defining anopening in said frame, said frame being molded from a resilient,thermoplastic material, each of said side members having one surfacedisposed in a common plane, a bead projecting above said one surface ofeach of said side members and extending along major portions of at leastone of said pairs of opposed side members, a stencil screen securedtosaid frame in overlying relation with said opening by fusion of saidbead to said stencil screen, one of said pairs of opposed side membersbeing substantially rigid, at least one of the side members of thesecond of said opposed side members being an outwardly bowed side memberwhich is adapted to be flexed inwardly while said stencil screen issecured to said frame, said outwardly bowed side member when releasedserving to maintain said stencil screen in a taut condition.

10. The stencil screen assembly of claim 9 wherein said head extendscompletely around the periphery of said opening.

11. In a stencil screen frame assembly, the combination comprising astencil screen frame including a plurality of normally straightresilient wall members defining an opening in said frame, means forsecuring a stencil screen to said frame in loose overlying relation withsaid opening, and rigid frame means insertable within the opening ofsaid stencil screen frame including outwardly bowed opposed side membersengaged .with a pair of said resilient Wall members whereby said pair ofresilient wall members are bowed outwardly to stretch said stencilscreen frame into a taut condition.

References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS634,954

'1 62 Canada. 718,839 3/42 Germany. 620,629 3 49 Great Britain.

WILLIAM B. PENN, Primary Examiner.

DAVID KLEIN, Examiner.

1. A GENERALLY RECTANGULAR STENCIL SCREEN FRAME COMPRISING A PLURALITYOF GENERALLY FLATTENED, RESILIENT WALL MEMBERS DEFINING AN OPENING INSAID FRAME, ONE OPPOSED PAIR OF SAID WALL MEMBERS BEING SUBSTANTIALLYRIGID, THE REMAINING OPPOSED PAIR OF SAID SIDE WALL MEMBERS BEINGNORMALLY OUTWARDLY BOWED MEANS INTEGRAL WITH SAID FRAME FOR SECURING ASTENCIL SCREEN TO SAID WALL MEMBERS IN OVERLYING RELATION WITH SAIDOPENING, SAID WALL MEMBERS BEING SUBSTANTIALLY PERPENDICULAR TO THEPLANE OF SAID STENCIL SCREEN AND COOPERATING THEREWITH TO DEFINE A WELLFOR RECEIVING A PRINTING MEDIUM, SAID REMAINING OPPOSED PAIR OF SAIDWALL MEMBERS BEING ADAPTED TO BE FLEXED INWARDLY WHILE SAID STENCILSCREEN IS SECURED TO SAID FRAME, SAID REMAINING OPPOSED PAIR OF SAIDWALL MEMBERS WHEN RELEASED SERVING TO MAINTAIN SAID STENCIL SCREEN IN ATAUT CONDITION.